1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display and its display-controlling method capable of decreasing the electric power consumption without damaging the display quality of a liquid crystal display unit.
2. Description of the Related Art
A liquid crystal display, of matrix type has been widely used as a display of a personal computer and the like, because it is thin and light and its electric power consumption is small. Recently, the liquid crystal display of matrix type, especially having low electric power consumption is positively developed because of environmental problem and the other needs.
FIG. 5 is a view showing the structure of a liquid crystal display disclosed in Japanese Patent Publication (Kokai) No. Heisei 10-312175. As illustrated in FIG. 5, this display comprises a matrix board 101, a plurality of pixel electrodes 102 provided on this matrix board in a shape of matrix, signal lines 103 interposed between these pixel electrodes, gate lines 104 interposed between the pixel electrodes in a direction different from that of the signal lines, switching elements 105 disposed between the pixel electrodes and the signal lines and on/off controlled by the gate lines, a driving circuit 106 for driving the signal lines based on input data, and a controller 107 for controlling the driving circuit 106.
This liquid crystal display is further provided with switching means 108 in every (n) signal lines, which are the lines for supplying the input data to the signal lines 103, so as to decrease the number of data to be sent from the driving circuit 106 to the display matrix board 101, for decreasing the electric power consumption, by the on/off operation of this switching means 108.
This conventional liquid crystal display, however, is provided with one switching means 108 per n signal lines 103, and therefore, one for n signal lines, namely, at least one for two is always switched off, regardless of the state of an image. Therefore, although the electric power consumption is surely decreased, the quality of images may be deteriorated depending on a display state of the images. Especially, in the case of displaying a moving picture, since the display screen is frequently changed, it is necessary to keep the high quality of the images. The conventional display as shown in FIG. 5, however, may not satisfy the needs.
In order to solve the problem, an object of the present invention is to provide a liquid crystal display and its display-controlling method capable of keeping the quality of images required according to the display state on a screen and capable of decreasing the electric power consumption.
According to one aspect of the invention, a liquid crystal display provided with a liquid crystal display unit with pixels disposed on a board in a shape of matrix, driver means for supplying a signal to the respective pixels based on display data so to display an image, and control means for controlling the driver means, the display comprises
switching means provided in every signal line for supplying a signal from the driver means to the respective pixels, and
liquid crystal display state judging means for judging display state on the liquid crystal display,
the switching means being on-off controlled based on the result judged by the liquid crystal display state judging means.
The liquid crystal display of the present invention is provided with switching means in the respective signal lines for supplying signals from the driver means to the respective pixels, and display judging means for judging the display state on a liquid crystal display unit. Therefore, after the display judging means judges the display state on the liquid crystal display unit, the number of signal lines for supplying the display data can be selected according to the judgment result. Namely, since it is possible to adjust the number of signal lines to be switched off, depending on the necessity, this liquid crystal display can decrease the electric power consumption, in accordance with a change of the data to be displayed on the liquid crystal display unit, without deteriorating the display quality.
In the preferred construction, the liquid crystal display further comprises memory means of storing switching timing data for on-off controlling the switching means as for the display state on the liquid crystal display unit.
Thus, the liquid crystal display of the present invention is provided with memory means, where switching timings suitable to various display states are stored, and it can select the switching timing suitable to the display state judged by the display state judging means so to switch the signal lines according to the same timing. As a result, the signal lines can be thinned out at the timing suitable to the display state.
In another preferred construction, the liquid crystal display unit is driven by active matrix drive system.
In the liquid crystal display of the present invention, when the liquid crystal display unit is formed in an active matrix type, a pixel may be formed by a TFT (Thin Film Transistor). Forming a pixel by a thin film transistor can realize a superior liquid crystal display in contrast, display of gradation, and response speed.
In another preferred construction, TFTs (Thin Film Transistors) are provided as for the respective pixels.
In another preferred construction, the liquid crystal display unit is driven by simple matrix drive system.
In another preferred construction, second memory means for temporarily storing display data information to be displayed on the liquid crystal display unit is provided in the driver means, and the liquid crystal display judging means judges the display state on the liquid crystal display unit, according to a change of the display data in the second memory means.
According to the liquid crystal display of the present invention, a change in the ratio of the number of display pixels to the number of the whole pixels, corresponding to a time change of the display data information, is calculated, so to judge the display state on the liquid crystal display unit. For example, when a change in the ratio of the number of the display pixels to the number of the whole pixels is high, the display state on the liquid crystal display unit can be judged to vary frequently, and when it is low, the display state can be judged to be stable.
In another preferred construction, the liquid crystal display further comprises memory means of storing switching timing data for on-off controlling the switching means as for the display state on the liquid crystal display unit, second memory means for temporarily storing display data information to be displayed on the liquid crystal display unit, which is provided in the driver means, the liquid crystal display judging means judging the display state on the liquid crystal display unit, according to a change of the display data in the second memory means.
According to another aspect of the invention, a display controlling method of a liquid crystal display provided with a liquid crystal display unit with pixels disposed on a board in a shape of matrix, driver means for supplying a signal to the respective pixels based on display data so to display an image, and control means for controlling the driver means, the method comprising the following steps of
judging display state on the liquid crystal display unit by the liquid crystal display, and on-off controlling the switching means provided in each signal line for supplying a signal from the driver means to the respective pixels based on the above judgment result.
In the preferred construction, the display controlling method of a liquid crystal display comprising the following steps of
storing switching timing data for on-off controlling the switching means into the memory means, as for the display state on the liquid crystal display unit, and
on-off controlling the switching means based on the switching timing data.
In another preferred construction, the-display controlling method of a liquid crystal display comprising the following steps of
temporarily storing the display data information to be displayed on the liquid crystal display unit into the second memory means within the driver means, and
judging the display state on the liquid crystal display unit, according to a change of the display data in the second memory means.
In another preferred construction, the display controlling method of a liquid crystal display comprising the following steps of
storing switching timing data for on-off controlling the switching means into the memory means, as for the display state on the liquid crystal display unit,
on-off controlling the switching means based on the switching timing data,
temporarily storing the display data information to be displayed on the liquid crystal display unit into the second memory means within the driver means, and
judging the display state on the liquid crystal display unit, according to a change of the display data in the second memory means.
According to a still further aspect of the invention, a liquid crystal display provided with a liquid crystal display unit with pixels disposed on a board in a shape of matrix, driver which supplies a signal to the respective pixels based on display data so to display an image, and controller which controls the driver, the display comprises
switching unit provided in every signal line which supplies a signal from the driver to the respective pixels, and
liquid crystal display state judging unit which judges display state on the liquid crystal display,
said switching unit being on-off controlled based on the result judged by said liquid crystal display state judging unit.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.